Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:5686830.

This clip can be used to hold any cord, cable, thin hose, tube item, or even LED string lights/Christmas lights. The .stl files come in different heights and lengths to fit varying sizes on the mounting area, which can be any flat protruding surface of at least 2 cm thickness (wood or metal fence, tabletop, shelf, brick pavers, etc.)

It's different from other clips since 1) the longer one tapers in the opening so it can grip and accommodate larger thicknesses, and 2) the holder for the cable or string is facing inward (towards the mounted surface) so that it hugs it and keeps it snug and secure. Outward facing holders (they're like small hooks) don't secure the cable or string and can result in them falling out of it.